Most studies agree on the detrimental effects of climate change on ecosystems as a whole, but what about the behavior of the species in them? A new study from Uppsala University researchers - the first of its kind in the world - reveals that coral bleaching and death can negatively affect how small reef fish learn about and avoid predators in coral reefs.:
Coral reefs are ecosystems that harbor hundreds of thousands of animals, giving them a home to thrive. However, the numerous stresses that coral reefs around the world now face cause habitat changes that, in turn, influence how the animals within these ecosystems interact.
In the new study, the team found that coral death and degradation altered the way that common damselfish respond to the chemicals that indicate the presence of predators.
"Baby fish use chemical alarm signals released from the skin of attacked individuals to learn the identity of new predators," said Mark McCormick of James Cook University and first author of the study. "By pairing the alarm cue from their wounded buddy with the smell or sight of the responsible predator, fish are able to learn which individuals are dangerous and should be avoided in the future."
However, when corals die and become covered in algae - a process called coral bleaching - the olfactory landscape of the reef changes, which negatively impacts the aforementioned learning mechanisms that are used by some fish to survive.
The team found that the smell of an injured fish paired with a predator taught the ambon damselfish to learn to avoid new predators on live coral. However, when the fish lived on dead coral, they did not respond to or learn any of the predator cues.
Further analysis revealed that another species that exclusively lives on dead coral was still able to identify novel predators using chemical cues whether the coral was dead or alive.
"If the process of cataloguing and avoiding predators is hindered in some species by coral degradation and loss, then much of the diversity of reef fish could be lost too," said Oona Lönnstedt of Uppsala University and senior author of the study. "Many reef fish need specific habitats that only healthy coral reefs can provide."
With the Great Barrier Reef currently experiencing the worst mass coral bleaching in its history, the new findings suggest that the fishes within the ecosystem could face numerous challenges.
"If dead coral masks key chemical signals used to learn new predators, the replenishment of reefs could be seriously threatened," Lönnstedt said.
The findings were published May 11 in the journal Proceedings of the Royal Society B: Biological Sciences.
